Urea and green tea like precursors for the preparation of g-C3N4 based carbon nanomaterials (CNMs) composites as photocatalysts for photodegradation of pollutants under UV light irradiation

Scavenging of Organic Pollutant and Fuel Generation through Cost-Effective and Abundantly Accessible Rust: A Theoretical Support with DFT Simulations

Waste management and energy generation are the foremost concerns due to their direct relationship with biological species and the environment. Herein, we report the utilization of iron rust (inorganic pollutant) as a photocatalyst for the photodegradation of methylene blue (MB) dye (organic pollutant) under visible light (economic) and water oxidation (energy generation). Iron rust was collected from metallic pipes and calcined in the furnace at 700 °C for 3 h to remove the moisture/volatile content. The uncalcined and calcined rust NPs are characterized through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier-transform infrared (FTIR) analysis, X-ray Diffraction (XRD), and thermogravimetric analysis (TGA). The morphological study illustrated that the shape of uncalcined and calcined iron rust is spongy, porous, and agglomerated. The XRD and DLS particle sizes are in a few hundred nanometers range. The photodegradation (PD) investigation shows that calcined rust NPs are potent for the PD of modeled MB, and the degradation efficiency was about 94% in a very short time of 11 min. The photoelectrochemical (PEC) measurements revealed that calcined rust NPs are more active than uncalcined rust under simulated 1 SUN illumination with the respective photocurrent densities of ~0.40 and ~0.32 mA/cm². The density functional theory simulations show the chemisorption of dye molecules over the catalyst surface, which evinces the high catalytic activity of the catalyst. These results demonstrate that cheaper and abundantly available rust can be useful for environmental and energy applications.

A new approach to study the degradation of the organic pollutants by A-doped MxOy/B photocatalysts

This work presents a new approach and a comprehensive mechanism to study the kinetics of the photodegradation of the organic pollutants. The vital role of various operational factors on the degradation of the organic pollutants is explained using this method. The proposed approach is based on the simple strategies and a powerful computational method. Two new variables "the effective concentration of photon" (I_eff) and "the effective concentration of the reactive centers" (RC) are defined to better understand the effect of operational parameters on the organic pollutant photodegradation. The optimum conditions of the photocatalytic degradation can be determined with the help of this method. This approach was used to study the kinetics of photodegradation of the organic pollutants on the [Formula: see text] photocatalysts. The provided mechanism has been examined with the some experimental data. The high correlations between the experimental data and the fitting results under different conditions prove this mechanism could be reliable.

Efficient bacterial inactivation with S-doped g-C3N4 nanosheets under visible light irradiation

The pathogenic bacteria in water that threatens the human health and photocatalytic disinfection have been proven to be a cost-effective and promising green technology. It is significant and necessary to develop efficient, safe, and visible light-driven photocatalysts. In this study, Escherichia coli was used as model bacterium and the disinfection performance of prepared S-doped g-C₃N₄ nanosheets (S-CNNs) under visible light was investigated. The results showed that the synergistic effects of S doping and the unique 2D structure of S-CNNs enhanced the visible light absorption, enlarged the specific surface area and reduced the recombination of photogenerated charge carriers which is beneficial for promoting the photocatalytic disinfection of the E. coli. Scavenger experiments indicated •O₂^- and h⁺ were the predominant reactive species in the photocatalytic disinfection process. In addition, the kinetics of disinfection activity were fitted by the modified Hom model and the k₂ value of S-CNNs is 0.0219 min^-1, which is much higher than that of the bulk g-C₃N₄ (CN). This work has demonstrated efficient bacterial inactivation with S-CNNs under visible light irradiation.

Insight into the photodegradation mechanism of bisphenol-A by oxygen doped mesoporous carbon nitride under visible light irradiation and DFT calculations

Oxygen doped mesoporous carbon nitride (O-MCN) was successfully synthesized through one-step thermal polymerization of urea and glucose utilizing nanodisc silica (NDS) from rice husk ash as a hard template. The CO2 gas, NH3 and water vapor produced during the thermal process reshaped the morphology and textural properties of the of O-MCN compared to pristine mesoporous carbon nitride (MCN). Highest bisphenol A (BPA) removal achieved under visible light irradiation was 97%, with 60% mineralization ([BPA] = 10 mg L-1: catalyst dosage = 40 mg L-1; pH = 10; 180 min). In addition to mesoporosity, the sub-gap impurity states created from the oxygen doping reduced recombination rate of photogenerated carriers. Holes (h+) and superoxide (O2˙-) were identified as the predominant active species responsible for the photodegradation process. The photodegradation route was proposed based on the intermediates detected by LC-time-of-flight/mass spectrometry (LC/TOF-MS). The Density of States (DOS) showed that oxygen doping resulted in a higher photoactivity due to the stronger localization and delocalization of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The adsorption pathway of the BPA on the O-MCN and MCN was successfully predicted using the DFT calculations, namely molecular electrostatic potential (MEP), global and local descriptors.

Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation

The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.

Sodium alkoxide-mediated g-C3N4 immobilized on a composite nanofibrous membrane for preferable photocatalytic activity

Sodium alkoxide-mediated g-C3N4 is presented to fabricate flexible electrospun polyacrylonitrile nanofibers for the first time.

Introduction of the Effective Photon Concentration Variable for Studying the Mechanism of Crystal Violet Photodegradation

In this work, we have proposed a new approach to study the mechanism of crystal violet (CV) photodegradation on TiO₂ surface using kinetic Monte Carlo simulation. The TiO₂ surface was considered as a set of reactive centers, which is essential in dye photodegradation. A new variable "the effective photon concentration" (I_eff ) is defined. A detailed chemical understanding of the photocatalytic reaction is provided. This approach provides a simple and effective method to find the optimal conditions of the studied system. This goal was achieved by investigating the effects of some operational parameters, including initial concentration of CV, pH, loading TiO₂ , light intensity and volume, on the degradation percent, and also, on the effective photon concentration. The perfect agreements between the experimental and simulated data at different conditions confirmed the proposed approach for describing the CV photodestruction. Also, the simulation results indicated that: (1) a significant fraction of the scattered UV irradiation into the reaction vessel does not lead to charge carrier generation; (2) the generation and recombination of charge carriers have crucial roles in the photodegradation. This is the first time that a method based on the reactive centers is employed to investigate the dye degradation by a photocatalyst.

Biomedical application of graphitic carbon nitrides: tissue depositionin vivo, induction of reactive oxygen species (ROS) and cell viability in tumor cells

The urgency for new materials in oncology is immediate. In this study we have developed the g-C₃N₄, a graphitic-like structure formed by periodically linked tris-s-triazine units. The g-C₃N₄has been synthesized by a simple and fast thermal process. XRD has shown the formation of the crystalline sheet with a compacted structure. The graphite-like structure and the functional groups have been shown by Raman and FTIR spectroscopy. TEM image and AFM revealed the porous composed of five or six C-N layers stacked. DRS and Photoluminescence analyses confirmed the structure with band gap of 2.87 eV and emission band at 448 nm in different wavelengths excitation conditions. The biological results showed inhibitory effect on cancer cell lines and non-toxic effect in normal cell lines. To the best of our knowledge, this is the first work demonstrating the cytotoxic effects of 2D g-C₃N₄in a cancer cell line, without any external or synergistic influence. The biodistribution/tissue accumulation showed that g-C₃N₄present a tendency to accumulation on the lung in the first 2 h, but after 24 h the profile of the biodistribution change and it is found mainly in the liver. Thus, 2D-g-C₃N₄showed great potential for the treatment of several cancer types.

Efficient Advanced Oxidation Process (AOP) for Photocatalytic Contaminant Degradation Using Exfoliated Metal-Free Graphitic Carbon Nitride and Visible Light-Emitting Diodes

The photocatalytic performance of metal-free graphitic carbon nitride (g-C3N4) was examined using visible light-emitting diodes (LEDs). A comparative and parametric study was conducted using the photocatalytic degradation of phenol as a model reaction. The g-C3N4 photocatalyst was synthesized from melamine using thermal condensation, followed by a thermal exfoliation that increases the catalyst surface area from 11 to 170 m2/g. Different characterization techniques, namely X-ray powder diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption using the Brunauer–Emmett–Teller method, ultraviolet-visible (UV–vis) spectroscopy, transmission electron microscopy, photoluminescence spectroscopy (PL), and zeta potential analysis, were used to characterize the photocatalyst. A comparison of the photodegradation experiments conducted with a full-spectrum xenon lamp and a custom-made single-wavelength LED immersion lamp showed that the photocatalyst performance was better with the LED immersion lamp. Furthermore, a comparison of the performance of exfoliated and bulk g-C3N4 revealed that exfoliated g-C3N4 completely degraded the pollutant in 90 min, whereas only 25% was degraded with bulk g-C3N4 in 180 min because the exfoliated g-C3N4 enhances the availability of active sites, which promotes the degradation of phenol. Experiments conducted at different pH have shown that acidic pH favors the degradation process. The exfoliated g-C3N4 has shown high photocatalytic performance in the photodegradation of other phenolic compounds, such as catechol, m-cresol, and xylenol, as well.